In Utero Intervention for Obstructive Uropathy: Assessing the Benefits
In Utero Intervention for Obstructive Uropathy: Assessing the Benefits
ABSTRACT & COMMENTARY
Synopsis: Antenatal surgical intervention in obstructive uropathy has been done for more than 15 years. The intent of this surgery is to divert urine from the fetal bladder to the amniotic space to prevent the pulmonary hypoplasia that results from oligohydramnios. The study group included 34 fetuses who underwent vesicoamniotic shunt placement over a nine-year period at the University of Michigan and Wayne State University. The object of the study was to assess the long-term outcome of these children. Freedman and colleagues conclude that the intervention may have benefited those with severe obstruction whose outcome is usually fatal.
Source: Freedman AL, et al. Long-term outcome in children after antenatal intervention for obstructive uropathies. Lancet 1999;354:374-377.
Freedman and colleagues reviewed the course of follow-up of 34 patients who underwent antenatal vesicoamniotic shunt placement following diagnosis of obstructive uropathy by ultrasonography. These fetuses were considered to be at high risk for pulmonary hypoplasia, which is frequently fatal and is believed to result from oligohydramnios. There is also concern regarding the role that intrauterine obstruction plays in the development of renal dysplasia and insufficiency, as well as impaired bladder function. The intent of the study was to assess the clinical outcomes of the children two or more years after shunt procedures performed from 1987-1996. Twenty-one children survived, 17 were older than 2 years, and 14 were available for follow-up. The mean age at follow-up was 54.3 months (range, 25-114). None of the children had severe respiratory disease, although six had received diagnoses of either asthma or chronic bronchitis. Eight children had either end-stage renal disease or chronic renal insufficiency and six children had voiding dysfunction. Poor growth was common, with 86% of the children’s height less than the 25th percentile and 50% less than the fifth percentile. Freedman et al conclude the intervention may have helped those fetuses with severe obstruction, achieving outcomes similar to children with less severe obstruction.
Comment by Thomas L. Kennedy, MD, FAAP
Whenever fetal surgery is performed, it gets our attention. Such procedures seem dramatic, daring, and, pardon the expression, "cutting edge." In the case of surgery for obstructive uropathy to divert fetal urine to the amniotic cavity, intervention seems to make good sense for two reasons. First, relief of urinary tract obstruction (almost invariably posterior urethral valves in males) should reduce the risk of pressure-induced renal injury and/or developmental dysplasia. Second, oligohydramnios is associated with pulmonary hypoplasia and restoration of amniotic fluid should prevent it. But does it? How effective is surgical intervention? And what are the long-term outcomes of these children?
It was in search of answers to these questions that this follow-up study was conducted. It should be noted that definitive conclusions cannot be reached since there was no control group, intervention occurred at widely different times of gestation (14.5-31 weeks), and the numbers are small. Nevertheless, the intent was to determine the health of the 62% who survived the neonatal period.
Assessment of two most affected organ systems, that is, respiratory and renal, immediately come to mind. On the positive side, despite the fact that several of the children carry pulmonary "diagnoses," none has serious limitations. More concerning, end-stage renal failure and/or chronic renal insufficiency occurred in six of 14, but Freedman et al caution that, in the majority, ongoing voiding dysfunction and/or urinary tract infections appear to have contributed significantly to progressive renal injury. An important prognostic indicator seems to be the minimum serum creatinine in the first year of life; all children with a creatinine level that never got below 1.0 mg/dL eventually required dialysis or transplantation. Freedman et al do not comment on the incidence of other renal complications such as hypertension or renal tubular acidosis, but the significant problems with growth that were identified may be secondary to chronic acidosis.
At any rate, children who undergo antenatal relief of urinary tract obstruction are not home free. The surgery itself is difficult and may be associated with fetal demise, premature birth, or failure of the shunt to stay in place. Furthermore, the problems that predate the surgery may cause renal and pulmonary damage not reversed by the surgery. In those who survive, multiple surgical procedures are sometimes necessary and even then, ongoing voiding problems may persist and continue to cause renal injury.
The take-away message is not that prenatal surgery for urinary tract obstruction should not be done, but that fetuses must be carefully selected, with intervention occurring in those with the most severe obstruction and as early in gestation as possible. However, identification of this group is not always easy, and relief of obstruction in these cases can lead to infant survival, although not always without significant post-natal problems.
Fetal urinary tract obstructions:
a. can often be relieved antenatally but surgery is associated with a 62% neonatal demise.
b. is most often caused by posterior uretheral valves.
c. require antenatal surgery, which is almost universally successful with few long-term sequellae.
d. should not be considered in fetuses with severe obstruction.
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